Rolling mill gauge control

ABSTRACT

A rolling mill gauge control system and method are disclosed for controlling the delivery thickness or gauge of a strip workpiece leaving one or more roll stands of a tandem rolling mill. The initial roll opening setting and the initial speed setting for each roll stand are typically provided by an operator or a schedule calculation computer system prior to the passage of the work strip through the roll stand. Assuming these initial speed settings are correct, the known mass flow operational condition of the work strip in relation to the last stand target delivery gauge is used to establish the initial desired mass flow delivery gauge from each controlled roll stand of the rolling mill in relation to the desired delivery gauge from the last roll stand. Then as the work strip passes through each successive roll stand, and before the work strip reaches the X-ray gauge measurement device following the last roll stand, the roll force determined actual delivery gauge from each roll stand is compared with the initial desired mass flow delivery gauge to determine a work strip gauge error leaving the latter roll stand, which gauge error is utilized for determining a desired correction in the roll opening setting for that roll stand before the work strip reaches the X-ray gauge device.

United States Patent Smith, Jr. July 1, 1975 ROLLING MILL GAUGE CONTROL[57] ABSTRACT [75] Inventor: Andrew W. Smith, Jr., Pittsburgh, A rollingmill gauge control system and method are Pa. disclosed for controllingthe delivery thickness or auge of a stri workpiece leavin one or moreroll [73] Asslgnee: .lestmghwse Electr'c Etands of a tandem rollingmill. The initial roll opening Pmsburgh setting and the initial speedsetting for each roll stand [22] Filed: Mar. 27, 1974 are typicallyprovided by an operator or a schedule calculation com uter s stem riorto the assa e of [2]] App! 455l59 the work strip tlFrough i he rollstand. Assur ning hese initial speed settings are correct, the knownmass flow [52] US. Cl. 72/11 operational condition of the work strip inrelation to [51] Int. Cl. B21b 37/08 the last stand target deliverygauge is used to establish [58] Field of Search 72/6-12, 16, the initialdesired mass flow delivery gauge from each 72/19, 20, 21 controlled rollstand of the rolling mill in relation to the desired delivery gauge fromthe last roll stand.

[56] References Cited Then as the work strip passes through eachsuccessive UNITED STATES PATENTS roll stand, and before the work stripreaches the X-ray 2 726 541 12/1958 Sims 73/885 gauge measurement fnowmgh last 3'232O84 H1966 Sims M 72/16 stand, the roll force determinedactual delivery gauge 3:332:263 7,1967 Beadle at 72/7 from each rollstand is compared with the initial de- 3,56l,237 2/1971 Eggers et a1.72/7 sired mass flow delivery gauge to determine a work 3,592,031 7/1971Sutton et a1. 72/8 strip gauge error leaving the latter roll stand,which 3,600,920 8/1971 Smith, Jr 72/8 gauge error is utilized fordetermining a desired cor- Primary ExaminerMilton S. Mehr Attorney,Agent, or Firm-R. G. Brodahl ROLL OPENING CONTROL n ROLL 4 POSITIONDETECTOR,

rection in the roll opening setting for that roll stand before the workstrip reaches the X-ray gauge device.

10 Claims, 8 Drawing Figures ROLL OPENING CONTROL X-RAY .GAUGE GAUGECONTROL SHEET ROLL OPENING CONTROL 2 Q D m F fl N r N I\ F s F M L M S 23 W. M H K e P r F m F N K lm n Z Cv I US ROU T P l r K GAUGE CONTROLKF(N) 2 u mm H R W W0 l LIT I C K m H S R H %D m MF(N) w QmOu 440m SHEETMm m SHEET 3 CONTROLLED ROLL LAST ROLL OPERATOR sTANDIl) STAND(LS)'fgxggi figfl H(LS) FsILsI MWEE T GEISGE DETERMINATION FPM(I)H(LS)-XFPM(LS)*FS(LS) FPM(I)X- Fsm H I Fm ROLL FORCE I COS(I) GAuGEHRFII) GAUGE ERROR M30) DETERMINATION 7 DETERMINATION PM K T)HRF(I)=MSD(I)+COS(I)+K(I)F(I) GEm-Hm ROLL OPENIN M30) DETERMINATION KU)Km GE) P(I) ,DELsI1I=-GE(1)*[ I] GDREEII) SDREF(I)=MSD(I)+DELS(I) IFIG.6

n nnnn n (I mm mm 3,892,112 SHEET 4.

FIGURE 3 E TABLISHING DESIRED DELIVERY GAGEaHI I III-0R EACH STAND P IORT8 ENTE ING FIRST STAND USING REFERENCE INITIAL STAND SPEED. FPM( I I!ND DESIRED DELIVERY GAGEJHILSI SET STAND CBUNTER IFI HI I I HILSHFPILSI'F ILSII (FP H I NFSI I I I LAST STAND CHECK IF I I IEQO L5) G5 TB100 GB TB 32 END FIGURE 4 c CALCULATE GAGE ERRBR GEN) AND SCREWDBWNREFERENCE soREFm TB CBNTRBL GAGE SET srmo CBUNTER hrs DETERMINE GAGEERROR -I I I I 1*'(I (2+I'1F( I I I 1 "EXP I K3+MFI I I I I HRF I I HSD(I I +C6S( I H-KF' 1 1 EII IBHRH I I-H( I I DETERMINE ROLL. BPENINGCBRRECTIBN DEL I I ='GE( I I r (K( I I/P( I I )+1 I LIMIT AND BUPU RBLLD ENI PBSITIBN REFERENCE SDREFI I I MSDI I I+DEL$I I I L ST STAND CHECKIFII -E LSI E T6 100 I I *1 66 TB 32 END Hes ROLLING MILL GAUGE CONTROLBACKGROUND OF THE INVENTION The present invention relates to tandemmetal workpiece reduction rolling mills and more particularly to suchrolling mills including roll force sensing load cells operative withselected roll stands for controlling the delivery gauge of the workstrip leaving those roll stands.

In the operation of a metal rolling mill, the unloaded roll opening andthe speed of each roll stand are initially set up, before the work stripenters that roll stand, either by an operator or by a schedulecalculation control computer to produce a work strip reduction resultingin a desired on-gauge finished work product leaving that roll stand. Itis usually assumed that the loaded roll opening'of a roll stand equalsthe stand delivery gauge, since there is little or no elastic workpiecerecovery.

Because the provided roll stand set up conditions may be in error andsince certain mill parameters affect the stand loaded roll openingduring the actual rolling operation, a stand gauge control system isemployed to control the stand delivery gauge.

The well known roll force gauge control system has been used to providedesired gauge control operation (the workpiece thickness is alsosometimes spelled gage) for one or more stands of tandem rolling mills,using Hookes law for controlling the roll opening position at a givenroll stand. The loaded roll opening and hence the work strip deliverygauge from that given roll stand, under normal workpiece rollingconditions, equals the unloaded roll opening position plus the millstand spring stretch caused by the roll separating force applied to thework rolls by the workpiece. The roll separating force is measured by aload cell or other suitable force detecting device operative with theroll stand. The roll opening position is then controlled to balance rollforce changes from a reference or initial lock on value and thereby tohold the loaded roll opening at a substantially constant value. Thefollowing formula relationship can be used to establish the deliverygauge of the work strip leaving a controlled roll stand where h is theloaded roll opening and the delivery gauge of the work strip, S is theunloaded roll opening position, and K is the roll stand mill springconstant multiplied by F, the measured roll separating force. Theasterisk is the well known Fortran programming symbol formultiplication.

A typical prior art roll force gauge control system for a roll stand isan analog feedback system operative to make a comparison of thedetermined work strip delivery gauge with a desired reference gaugeleaving the roll stand, and responsive to measured stand roll force andmeasured roll opening position to control the roll opening position inaccordance with the following error condition AS K AF where AS is theerror in roll opening position to be corrected in relation to areference roll opening position and AF is the measured change in rollforce from a desired force reference and K is the roll stand mill springconstant.

Once the unloaded roll opening position and stand speed initial setupshave been determined and made by either a mill operator or a schedulecalculation computer system for a particular work strip passage throughthe roll stands to effect a desired gauge reduction, the actual rollingoperation can be started and the controlled roll openings are thenregulated to provide the desired work strip delivery gauge from eachcontrolled roll stand of the rolling mill.

It is known in the prior art, as shown by U.S. Pat. No. 3,600,920 by thesame inventor, to recalibrate the roll opening control for a given rollstand, after the work strip has passed through all of the roll stands ofa tandem rolling mill, in relation to the last roll stand actualdelivery gauge as measured by an X-ray gauge positioned after the lastroll stand. The speed relationship of a given roll stand as compared tothe last roll stand is utilized to determine the mass flow actualdelivery gauge leaving that given roll stand. The difference between theroll force acutal delivery gauge of that given roll stand and the lattermass flow actual delivery gauge is utilized for recalibration of theroll opening control apparatus, such as a screwdown or hydraulicposition control mechanism, for that given roll stand.

The well known gauge meter or roll force gauge control system has beenwidely used to produce stand gauge control in metal rolling mills, andparticularly in tandem hot steel strip rolling mills and reversing platemills where experience has demostrated that roll force control isparticularly effective. Earlier publications and patents such as anarticle entitled Installation and Operating Experience with Computer andProgrammed Mill Controls by M. D. McMahon and M. A. Davis in the 1963Iron and Steel Engineer Yearbook at pages 726 and 733, an articleentitled Automatic Gauge Control for Modern I-Iot Strip Mills by J. W.Wallace in the December 1967 Iron and Steel Engineer at pages to 86, anarticle entitled Control Computer Teaches Itself To Roll Metals by A. W.Smith in the Westinghouse Engineer for July 1970 at pages 108 to 113,U.S. Pat. No. 3,561,237 issued Jan. 9, 1971 to Eggers et al. and U.S.Pat. No. 2,726,541, issued Dec. 13, 1955 to R. B. Sims describe thetheory upon which operation of the roll force and related gauge controlsystems is based. Attention is also called to U.S. Pat. No. 3,568,637issued Mar. 9, 1971, U.S. Pat. Nos. 3,574,279 and 3,574,280 issued Apr.13, 1971 to A. W. Smith, which relate to roll force automatic gaugecontrol systems.

SUMMARY OF THE INVENTION In accordance with the principles of thepresent invention, a control system and method for controlling thedelivery gauge or thickness of workstrip product leaving one or moreroll standsof a tandem rolling mill includes the determination of themass flow target delivery gauge of the work strip for each controlledroll stand in relation to the last stand target delivery gauge beforethe workstrip has arrived at the X-ray gauge following the last rollstand, and then comparing the roll force determined actual deliverygauge for the same roll stand with this mass flow target delivery gaugeto establish a gauge error for correction by an adjustment of the rollopening position setting for that roll stand.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic diagram of aroll force gauge control arranged for operation with a tandem rollingmill in accordance with the present invention;

FIG. 2 shows a curve to illustrate the mill spring characteristic for atypical roll stand in relation to the determination of the stretch of acontrolled roll stand;

FIG. 3 shows a flow chart to illustrate the determination of mass flowtarget delivery gauge for each roll stand before a given work strippasses through the rolling mill;

FIG. 4 shows a flow chart to illustrate the determination of the gaugeerror and roll opening position reference for each controlled rollstand;

FIG. 5 is a functional illustration of the control of workstrip deliverygauge from a roll stand in accordance with the present invention;

FIG. 6 illustrates the situation where the tail end of a previous workstrip and the head end of a subsequent work strip are passing throughthe rolling mill at the same time;

FIG. 7 shows a program listing prepared in relation to the flow chart ofFIG. 3; and

FIG. 8 shows a program listing prepared in relatio to the flow cart ofFIG. 4.

GENERAL DESCRIPTION OF THE GAUGE CONTROL SYSTEM AND ITS OPERATION Thereis shown in FIG. 1 a controlled four high rolling mill stand S(N)operative with a gauge control 12 in accordance with the principles ofthe present invention. Generally, the invention is applicable to controlthe operation of one or more tandem rolling mill stands for which rollforce gauge control is employed. The tandem rolling mill shown in FIG; 1includes a last stand S(LS).

A workpiece 2 enters the roll stand S(N) at the entry end and it isreduced in thickness and transported through the succeeding roll standsto the delivery end of the rolling mill. The entry workpiece would be ofknown steel grade and it typically would have a known gauge orthickness. The delivered workpiece would have a desired target gauge orthickness H(LS) based upon the production order for which it isintended.

In the reduction rolling process, the succeeding roll stands operate atsuccessively higher speeds to maintain proper workpiece mass flow. Eachstand produces a predetermined reduction or draft such that the totalmill draft reduces the entry workpiece to strip with the desired gaugeor thickness.

Each stand is conventionally provided with a pair of back-up rolls 4 and6 and a pair of work rolls 8 and 10 between which the workpiece 2 ispassed. A large DC drive motor 11 is controllably energized at eachstand to drive the corresponding work rolls at a controlled speed.

In relation to roll stand S(N), the sum of the unloaded work rollopening MSD(N) and the mill stretch K(N) AF(N) substantially defines theroll force determined workpiece gauge I-IRF(N) delivered from thecontrolled roll stand S(N) in accordance with Hookes law. A well knowncalibration offset COS(N) can be included to provide desired calibrationof the roll opening control apparatus operative with the roll standS(N), which roll opening control apparatus could be a pair of screwdownmotors or a hydraulic positioning apparatus, to position the back-uprolls and thereby apply pressure to the work rolls. A conventional rollopening position detector 14 provides an electrical signalrepresentation MSD(N) of the unloaded roll opening position. Roll forcedetection is provided at the roll stand S(N) by a conventional load cell16 which generates an electrical analog signal F(N) proportional to theroll separating force between the work rolls. A speed sensing transducer18, such as a pulse transducer, generatesa stand speed signal FPM(N).

The gauge control 12 provides automatic gauge or thickness for theoperation of the mill stand S(N). The gauge control 12 can include aprogrammed general purpose process control digital computer system,which is interfaced with the various mill operational sensors and thevarious mill control devices to provide control over the operation ofthe mill stand S(N). According to user preference, the gauge control 12can also include well known and conventional manual and- ,/or automaticanalog controls for back-up operation in performing other preselectedmill functions.

On the basis of these considerations, a suitable digital computer systemfor the on-line roll force gauge control system 12 would be a Prodac2000 (P2000) sold by Westinghouse Electric Corporation. A descriptivebook entitled Prodac 2000 Computer Systems Reference Manual has beenpublished in 1970 by Westinghouse Electric Corporation and madeavailable for the purpose of describing in greater detail this computersystem and its operation.

The digital computer system is associated with well known predeterminedinput systems, typically including a conventional contact closure inputsystem which scans contact or other signals representing the sensedstatus of various process operating conditions, a conventional analoginput system which scans and converts process analog signals, andoperator controlled and other information input devices and systems suchas paper tape, teletypewriter and dial input systems. Various kinds ofinformation can be entered into the computer system through the inputdevices including, for example, desired strip delivery gauge H(LS) andtemperature, strip entry gauge and width and temperature (by entrydetectors if desired), grade of steel being rolled, plasticity P tables,hardware oriented programs and control programs for the programmingsystem, and so forth. The contact closure input systems and the analoginput systems interface the computer system with the process through themedium of measured or detected variables, which include the following:

1. A roll force signal F(N) from the load cell 16 at the roll stand S(N)proportional to stand roll separating force for use in roll force gaugecontrol.

2. Roll opening position signal MSD(N) generated by the respectiveposition detector 14 for use in roll force gauge control.

3. A roll stand speed signal FPM(N) from a pulse generator 18 operativewith the drive motor 11 of the controlled roll stand S(N).

4. A roll stand speed signal FPM(LS) from a pulse generator 17 operativewith the drive motor 19 of the last roll stand S(LS).

It is noted at this point in the description, that the measured standroll force and the measured stand roll opening position in relation tothe workpiece head end are stored and used as references for roll forcegauge control system functioning, if it is desired to operate in thewell known lock-on mode of roll force gauge control operation.

To effect determined output control actions, controlled devices areoperated directly by means of output system contact closures or by meansof analog signals derived from output system contact closure through adigital to analog converter. The principal control action outputs fromthe gauge control 12 includes a positioning command signal SDREF(N)applied to the roll opening control 15 for the controlled roll stand8(1) and other controlled roll stands, and a speed control signalapplied to the drive motor 11 of roll stand S(N) and the other rollstands in accordance with respective desired speed setting for mass flowoperational conditions.

Display and printout systems such as numeral display, tape punch, andteletypewriter systems also can be associated with the outputs of thedigital computer gauge control system in order to keep the mill operatorgenerally informed about the mill operation and in order to signal theoperator regarding an event or alarm condition which may require someaction on his part.

Generally, the gauge control 12 uses Hookes law to determine the totalamount of screwdown movement required at the roll force controlled standS(N) at the calculating point in time for roll force and gauge errorcorrection, i.e. forloaded roll opening and stand delivery gaugecorrection to the desired value. The calculation defines the totalchange in the unloaded roll opening position setting required to correctfor determined gauge error causing conditions.

As well known to persons skilled in this art, the desired roll openingcorrection DELS(N) in relation to controlled roll stand S(N) iscalculated to enable roll force gauge control operation in accordancewith the following programmed relationship algorithm:

where:

GE(N) gauge error of controlled roll stand S(N) K(N) stand S(N) millspring constant (in/l0 lb.)

P(N) workpiece plasticity (in/ lb.) in relation to stand S(N).

Generally the operative value of each stand spring constant K isrelatively accurately known. It is first determined by the well knownwork roll screwdown test, and it can be recalculated if desired prior toeach workpiece pass on the basis of the workpiece width and the backuproll diameter. Each resultant spring curve is stored for on-line gaugecontrol use.

The operative value of the workpiece plasticity P at each roll stand isalso relatively accurately determined. If desired, P tables can bestored in the storage memory of the digital computer system associatedwith the gauge control 12 to identify the various values of P whichapply to the controlled roll stand S(N) for various grade class andgauge class workpieces under various operating conditions and at variousoperating times during the rolling of the workpiece strip 2.

A main advantage of using the roll force gauge control system is theability to detect error changes in strip gauge the instant they takeplace as the product is being rolled in the roll stand. A change instrip delivery gauge or thickness can be caused by a change in entrythickness, or a change in hardness as usually caused by a change intemperature. This change in delivery gauge can be immediately detectedby feedback information monitoring of the roll separating force on theroll stand.

There is shown in FIG. 2 a curve to illustrate the typical mill springcharacteristic for a roll stand, such as controlled roll stand S(N). Thecurve is a plot of measured roll force MF(N) for a typical roll stand(N) against the resulting stretch KF(N) of the roll stand, or theproduct of K(N) the stand spring constant and P(N) the stand roll force.The curve shown in FIG. 2 can be mathematically represented by therelationship.

where K K and K are constants established by data collecting and curvefitting techniques well known and practiced for several years by personsskilled in this art. The curve is established by closing together thestand work rolls, through operation of the roll opening control of theroll stand, until some minimum roll force is sensed by the stand loadcell, and then progressively closing the work rolls by predeterminedincremental settings and reading the corresponding roll force for eachsuch setting. Then, knowing the mill spring characteristic curve for agiven roll stand of the rolling mill, the values of constants K K and Kfor that roll stand are determined by well known curve fittingtechniques. It should be noted in relation to above equation (4) thatthe double asterisk represents the well known Fortran programming symbolfor an exponential and the single asterisk indicates multiplication.

There is shown in FIG. 3 the flow chart of a program utilized todetermine the mass flow target delivery gauge for each controlled rollstand, such as roll stand S(I), where I is a roll stand index, beforethe work strip has passed through the rolling mill and become operativewith the X-ray gauge positioned after the last roll stand S(LS). At step20 a stand counter is initially set to one. At step 22 the mass flowtarget delivery gauge is determined for a given roll stand (I)successively indexed by the stand counter, firstly such as roll standone and then secondly roll stand two and so forth. At step 24 a check ismade to see if that given roll stand (I) is the last stand, and if it isnot the program goes to step 26 where the stand index I is incrementedby one to the next succeeding roll stand, and steps 22 and 24 arerepeated until the check at step 24 indicates that index stand I is nowthe last roll stand S(LS), when the program operation ends.

There is shown in FIG. 4 the flow chart of a program utilized todetermine the gauge error and roll opening position reference for eachcontrolled rollstand of the rolling mill in accordance withthe presentinvention, after the work strip has entered the first roll stand andbefore the work strip reaches the X-ray gauge positioned after the lastroll stand S(LS). At step 30 the stand index counter is set to one. Atstep 32, the mill stretch KF(I) for the indexed roll stand (I) isdetermined in accordance with above equation (4). Then the roll forcedetermined actual delivery gauge I-IRF(I) leaving the roll stand (I) isdetermined in accordance with the well known relationship:

HRF(I) MSD(I) COS(I) KF(I) where MSD(I) is the unloaded roll openingposition "error GE( I) for' roll stand (I) is determined by therelationship: e I

GE(I) HRF(I) H(l) where H(I) is the mass flow target delivery gauge forindexed rollstand (1) determined at step 22 of the program flow chartshown in FIG. 3 and HRF (I) is the roll force actual delivery gaugeleaving roll stand (I). At step 34 the roll opening correction DELS(I)for roll stand (I )is determined in accordance with the relationship ofabove equation (3), where roll stand (N) is how the index roll stand(I). At step 36 the roll opening position reference for indexed rollstand (I) is established by the'relationship:

a e SDREF(I).= MSD(I) DELS(I) where M SD(I )is the present unloaded rollopening position setting for roll and stand (I) and DELS(I) is thedesired roll opening correction for roll stand (I), which roll openingposition reference SDREF (I can be limit checked and output to the rollopening control apparams for index roll stand (I). At step 38 a check ismade to see if roll stand (I) is the last stand of the rolling mill, andif not at step 40 the index (I) is incremented by one and thepro'gramstep 32, 34 and 36 are repeated for succeeding roll stands ofthe rolling mill until the index roll stand (I) is the last roll stand(LS), when the program operation ends. The'pro gram illustrated by FIG.3 is intended'to be signal for stability and related control systempractical operation reasons.

run just before each work strip enters the first roll stand of therolling mill, as can be monitored by well known work strip positionsensing tranducer'devices. The program illustrated by FIG. 4 is intendedto be run periodicfally, such as five times per second, for allcontrolled 7 up speed reference FPM(LS) for the last roll stand (LS )andtheinitial target delivery gauge H(LS) leaving the last roll stand (LS).The forward slip characteristic FS (I) for the controlled roll stand (I)and the forward slip character istics FS(LS) for the last roll stand(LS) arie predetermined and supplied byv the operator. At

step '52 the'roll force determined actual delivery gauge,

I-IRF(I) leaving controlled roll stand (I) is established after the workstrip is passing through the roll stand (I). At step 54 the gauge errorGE(I) in the work strip leaving roll stand (I) is determined. At step 56the roll opening correction DELS(I) and the associated roll openingposition reference SDREF(I) are determined,

with the position reference signal being output to the controlled rollstand (I), after limiting this reference The process control programsare organized in away to accommodate the normal mill condition where thehead end of one succeeding workpiece is entering the early stands whilethe 'tail end of the previous workpiece is still being rolled in thelater stands. This conditionis shown in FIG. 6 where workpiece A isbeing rolled in stands S4 and S5 when the new workpiece B is in standsS1 and S2. It is necessary that the initial stand speeds, roll openingsand desired delivery gauge be established by the operator or by theschedule calculation computer prior to the entry of the new workpieceinto stand S1 so that the mill setups may be changed to the new value assoon as the tail end of the previous workpiece leaves a particularstand. Just prior to the entry of the new workpiece into a first stand,the initial speed FPM(I) and desired target gauge or thickness H(LS) areused to determine the desired gauge from each stand as shown in FIG. 3so that the desired gauge H(I) is available for the gauge errordetermination as shown in 4.

' This gauge error and screwdown reference calculation is initiated assoon as a workpiece enters a stand and repeated periodically (such asfive times per second) until the workpiece leaves the stand.

, For instance, under the conditions shown in FIG. 6, the gauge errorand screwdown reference calculations shown in FIG. 4 are being performedfor workpiece A with a first stand FS value of 4 and a last stand LSvalue of 5. The same calculations are used to control the gauge ofworkpiece B in stands S1 and S1 by using a first stand FS value of 1 andat last stand LS value of 2. Each setof calculations used the desiredstand delivery gauge H(I) value that was established by the procedureshown in FIG. 3 for that particular workpiece prior to its entry intothe mill.

In FIGS. 7 and 8 there are included two instruction program listingsthat have been prepared to determine the roll force automatic gaugecontrol operation of a tandem rolling mill in accordance with the heredisclosed control system and method. The instruction program listingsare written in Fortran language suitable for use with the PRODAC P2000digital computer system, which is sold by Westinghouse ElectricCorporation for real time process control computer applications. Many ofthese digital computer systems have already been supplied to'customers,including computer instruction books and descriptive documentation toexplain to persons skilled in this art the operation of the hardwarelogic and the executive software of this digital computer system..Theinstruction program listings are included to provide an illustration ofone suitable embodiment of the present control system and method thathas acutally been prepared. The instruction program listings have notbeen debugged through the course of extensive practical operation forthe real time control'of a rolling mill. It is well known by personsskilled in this art that most real time process control ap- 1. A methodof controlling the delivery gauge of a work strip passing through atleast one roll stand of a tandem rolling mill in accordance with adesired delivery gauge leaving the last rolling stand of said rollingmill, with said one roll stand having a pair of work rolls and a rollforce measurement device, said method including the steps ofestablishing a target delivery gauge for said work strip leaving saidone roll stand in relation to said desired delivery gauge, the speedsetting of said one roll stand and the speed setting of the last rollstand, establishing the actual delivery gauge of said work strip leavingsaid one roll stand in relation to the measured roll force of said oneroll stand,

comparing said target delivery gauge with said actual delivery gauge todetermine a work strip gauge error leaving said one roll stand, and

establishing the roll opening between said pair of work rolls of saidone roll stand in relation to said gauge error.

2. The method of claim 1, with said target delivery gauge beingestablished in accordance with the mass flow relationship including thespeed setting of the last roll stand of said rolling mill before saidwork strip passes through said last roll stand.

3. The method of claim 1, with said target delivery gauge beingestablished before said work strip passes through the last roll stand ofsaid rolling mill.

4. The method of claim 1, with said target delivery gauge beingestablished in relation to the operation of the last roll stand andbefore the work strip passes through the last roll stand of the rollingmill.

5. The method of claim 1, with said target delivery gauge beingestablished before said work strip passes through the last roll stand ofsaid rolling mill and with said actual delivery gauge being establishedafter said work strip passes through said one roll stand.

' 6. In an apparatus for controlling the delivery gauge of a work strippassing through at least one roll stand of a tandem rolling mill havinga plurality of roll stands and in accordance with the desired deliverygauge leaving the last roll stand of said rolling mill, with said oneroll stand having a pair of work rolls and a roll force measurementdevice, the combination of means for determining a desired deliverygauge of said one roll stand in relation to said desired delivery gauge,the speed setting of said one roll stand and the speed setting of saidlast roll stand,

means for determining the actual delivery gauge of said one roll standin relation to a predetermined operation of said one roll stand, meansfor determining a gauge error in the work strip leaving said one rollstand in relation to said desired delivery gauge of said one roll standand said actual delivery gauge of said one roll stand and,

means for controlling the roll opening setting of said pair of workrolls of said one roll stand in relation to said gauge error.

7. The apparatus of claim 6, with said means for determining a desireddelivery gauge of said one roll stand being operative before said workstrip passes through the last roll stand of said rolling mill.

8. The apparatus of claim 6, with said means for determining the actualdelivery gauge of said one roll stand being operative after said workstrip passes through said one roll stand.

9. The apparatus of claim 6, with said desired delivery gauge of saidone roll stand being determined in relation to the speed setting of saidone roll stand before said work strip passes through said rolling mill.

10. The apparatus of claim 6, with said desired delivery gauge of saidone roll stand being determined before said work strip passes throughsaid rolling mill and with said actual delivery gauge of said one rollstand being determined after said work strip passes through said oneroll stand.

1. A method of controlling the delivery gauge of a work strip passingthrough at least one roll stand of a tandem rolling mill in accordancewith a desired delivery gauge leaving the last rolling stand of saidrolling mill, with said one roll stand having a pair of work rolls and aroll force measurement device, said method including the steps ofestablishing a target delivery gauge for said work strip leaving saidone roll stand in relation to said desired delivery gauge, the speedsetting of said one roll stand and the speed setting of the last rollstand, establishing the actual delivery gauge of said work strip leavingsaid one roll stand in relation to the measured roll force of said oneroll stand, comparing said target delivery gauge with said actualdelivery gauge to determine a work strip gauge error leaving said oneroll stand, and establishing the roll opening between said pair of workrolls of said one roll stand in relation to said gauge error.
 2. Themethod of claim 1, with said target delivery gauge being established inaccordance with the mass flow relationship including the speed settingof the last roll stand of said rolling mill before said work strippasses through said last roll stand.
 3. The method of claim 1, with saidtarget delivery gauge being established before said work strip passesthrough the last roll stand of said rolling mill. mill.
 4. The method ofclaim 1, with said target delivery gauge being established in relationto the operation of the last roll stand and before the work strip passesthrough the last roll stand of the rolling mill.
 5. The method of claim1, with said target delivery gauge being established before said workstrip passes through the last roll stand of said rolling mill and withsaid actual delivery gauge being established after said work strippasses through said one roll stand.
 6. In an apparatus for controllingthe delivery gauge of a work strip passing through at least one rollstand of a tandem rolling mill having a plurality of roll stands and inaccordance with the desired delivery gauge leaving the last roll standof said rolling mill, with said one roll stand having a pair of workrolls and a roll force measurement device, the combination of means fordetermining a desired delivery gauge of said one roll stand in relationto said desired delivery gauge, the speed setting of said one roll standand the speed setting of said last Roll stand, means for determining theactual delivery gauge of said one roll stand in relation to apredetermined operation of said one roll stand, means for determining agauge error in the work strip leaving said one roll stand in relation tosaid desired delivery gauge of said one roll stand and said actualdelivery gauge of said one roll stand and, means for controlling theroll opening setting of said pair of work rolls of said one roll standin relation to said gauge error.
 7. The apparatus of claim 6, with saidmeans for determining a desired delivery gauge of said one roll standbeing operative before said work strip passes through the last rollstand of said rolling mill.
 8. The apparatus of claim 6, with said meansfor determining the actual delivery gauge of said one roll stand beingoperative after said work strip passes through said one roll stand. 9.The apparatus of claim 6, with said desired delivery gauge of said oneroll stand being determined in relation to the speed setting of said oneroll stand before said work strip passes through said rolling mill. 10.The apparatus of claim 6, with said desired delivery gauge of said oneroll stand being determined before said work strip passes through saidrolling mill and with said actual delivery gauge of said one roll standbeing determined after said work strip passes through said one rollstand.